The primary goal of the Morphology Core Laboratory is to serve as a centralized, on-site resource to facilitate performance of morphologic, immunohistochemical, ultrastructural and morphometric studies needed for the proposed projects. This Core provides access to state-of-the-art instrumentation, technical assistance, instruction and consultation for PPG investigators conducting cell biological and morphologic studies at the cellular and ultrastructural level. Major equipment maintained within the Core includes a full range of light, confocal and electron microscopes; ancillary apparatus and preparative resources; as well as hardware and software for computer-assisted image, morphometric and densitometric analyses. The laboratory is staffed by well-qualified, experienced technicians, who will process tissues for light and transmission electron microscopy, including immunohistochemistry. Two members of the Core technical staff have received certification as histologists by the American Society of Clinical Pathologists. All procedures are standardized using written Standard Operating Procedures. All of the proposed projects will rely substantially on the resources available in this unit. The Specific Aims of this service core are to: 1) Prepare high-quality histologic sections for PPG investigators. 2) Provide access to a full range of optical instrumentation for morphologic investigation including light, confocal and electron microscopes; preparative devices; photographic equipment; CCD camera; and computer based image analysis, morphometry, and densitometry. 3) Provide technical assistance in all routine aspects of light and electron microscopy, specimen processing, computer assisted image analysis, morphometry, densitometry, and processing of images and micrographs. 4) Provide instruction in the use of instrumentation and consultation on experimental design, with specialized cytological and ultrastructural methods pertinent to particular projects. 5) Assist with development of new approaches to morphologic and morphometric analyses. 6) Perform toxicology studies according to GLP protocol required for pre-clinical studies to support applications for research permits from the FDA.